1. Field of the Invention
The present invention relates to a resist pattern-forming method, and a radiation-sensitive resin composition.
2. Discussion of the Background
Miniaturization of structures of various types of electronic devices such as semiconductor devices and liquid crystal devices has been accompanied by demands for miniaturization of resist patterns in lithography processes, and formation of fine resist patterns having a line width of about 90 nm using an ArF excimer laser that is a radioactive ray with a short wavelength has been investigated. Various compositions for resist capable of responding to radioactive rays having such short wavelengths have been studied. As such a composition for resist, a radiation-sensitive resin composition has been known which generates an acid at light-exposed sites by irradiation with a radioactive ray (i.e., exposure), and a catalytic action of the acid allows the difference in dissolution rates in developing solutions to be produced between the light-exposed site and the light-unexposed site, thereby enabling a resist patterns to be formed on a substrate.
On the other hand, as a technique for increasing a resolving power using a preexisting apparatus without increasing steps by utilizing characteristic features of such radiation-sensitive resin compositions, a technique in which an organic solvent having polarity lower than that of aqueous alkali solutions is used as a developer solution has been known (see Japanese Unexamined Patent Application, Publication No. 2000-199953). Attaining a high optical contrast is enabled when an organic solvent is used in this manner, and as a result, a fine pattern can be formed.
When a conventional radiation-sensitive resin composition is used in such a resist pattern-forming method in which an organic solvent is used as a developer solution, a film loss may be caused after resist pattern formation on the surface at light-exposed sites, resulting from use of an organic solvent as a developer solution. On the other hand, at light-exposed sites, a disadvantage of impaired etching resistance may also occur due to a decrease in the carbon content. Thus, achieving both superior etching resistance and inhibition of the film loss has been reportedly difficult. In addition, when the film loss is caused, improvement of lithography characteristics involving CDU (Critical Dimension Uniformity), MEEF (Mask Error Enhancement Factor) and resolution in fine regions, etc., has been difficult, which may result from the film loss. Accordingly, a radiation-sensitive resin composition and a resist pattern-forming method capable of improving these characteristics has been demanded.